EPR, optical, and dielectric spectroscopy of Er-doped cerium dioxide nanoparticles

Abstract

authoren Abstractauthoren The cerium dioxide nanoparticles doped at low level with Er ions and with grain sizes of about 22 and 300 nm were comprehensively studied using EPR, optical and microwave dielectric spectroscopy. The EPR observation of mainly cubic sites of Er3+ dopant in CeO2 reveals that vacancies are located more distant than the nearest neighbor position. This finding does not agree with recently published results based on density functional theory calculations. Time and spectral dependences of the permittivity of Er:CeO2 nanoparticles under UV laser excitation were studied by a Q‐band microwave resonance technique at the room temperature. The photoconductivity threshold for cerium dioxide nanoparticles has been estimated. The luminescence spectra for the nanocrystals in wide spectral range (λ= 240–1000 nm) were investigated. The anti‐Stokes emission of Er3+ ions under irradiation in 545–562 nm spectral range, stipulated by the thermally coupled 2H11/2 and 4S3/2 levels of Er3+ ions, has been observed. The UV irradiation (240–370 nm), which is not resonant with the 4f–4f transitions of Er3+ ions, excites emission of Er3+ ions due to the charge transfer from O2− to Ce4+ host ions and the subsequent energy transfer to Er3+ dopant ions.

EPR study of nanocrystalline CeO2 exhibiting ferromagnetism at room temperature

“…It should be noted that the g values of rare-earth ions in CeO 2 and CaF 2 single crystals are very close to each other [41,42]. EPR measurements of rare-earth ions in CeO 2 nanoparticles also confirm this [26,[43][44][45].…”

Surface modification of MPEG-b-PCL-based nanoparticles via oxidative self-polymerization of dopamine for malignant melanoma therapy

“…38,46,47 The size of NPs was 120-140 nm in diameter, which may result in highest cellular uptake by endocytosis and inhibit elimination by the RES, as well as promoting accumulation in tumor vasculature because of the enhanced permeability and retention effect on passive tumor targeting. 48,49 The size of the PTX-loaded MPEG-b-PCL NPs@PDA was larger than that of the nonmodified PTXloaded MPEG-b-PCL NPs; this could be ascribed to the coating of PDA on PTX-loaded NPs. The PDIs of PTX-loaded NPs and PTX-loaded NPs@PDA were 0.136 and 0.121, respectively.…”

Electron Magnetic Resonance (EMR) Technique and Nanoparticle Characterization

“…At the same time, mechanism for their cytotoxic effect is still to be understood. Recently reported study of Er 3+ doped CeO 2 nanoparticles [35] indicates the future scope for EMR of rare earth impurity doped oxide nanoparticles.…”

“…Rakhmatullin et al [35] have recently reported EMR characterization of CeO 2 : Er 3+ nanoparticles. The obtained results are compared with appropriated characteristics of the Er-doped CeO 2 single crystal and the macroscopic powder of commercial pure cerium dioxide.…”